1. Field of the Invention
The present invention relates to a multi-stage lens driving device, more particularly a miniature lens driving device that uses electromagnetic driving apparatus as power source to drive a miniature lens to engage in multi-stage position switch.
2. Description of the Prior Art
As shown in FIG. 1, a standard camera 1 comprises a lens set 11 and a sensor 12. The lens set 11 forms an image on sensor 12 by refracting the light rays from an object. If the distance between lens set 11 and sensor 12 is fixed (i.e. a fixed lens), the lens can only show clearly objects at its hyperfocal distance of 2-3 meters away. For the camera to shoot objects clearly at varying distances (for example at a close distance), a lens driving device is required to move the lens set, thereby adjusting the distance between lens set and sensor and achieving focusing.
When the lens set offers the zoom function, the multiple lenses in the lens set must be displaced in coordination with the change of zoom power. Thus the lens module is typically designed with a driving apparatus to displace the lenses.
The focusing or zooming mechanism for a conventional multi-stage camera lens moves the lens “manually”, which can be inconvenient at times. The present invention improves the aforesaid drawback by changing the lens driving method from manual to electromagnetic, and at the same time, reduce the size of lens driving device and simplify the design of lens module, hence lowering production costs and improving the assembly process. Such miniature lens driving device will be suitable for the camera module in cellular phone, notebook computer and PDA.
U.S. Pat. Nos. 5,150,260, 6,392,827, 5,220,461 and 5,471,100 have disclosed several techniques for driving lens, which however do not bear identical nor similar technical features as the ones disclosed in the present invention.